1. Field of the Invention
The present invention relates to a controller for switching between a long duct and a short duct for drawing intake air into an engine.
2. Description of the Related Art
A method is conventionally known to detect a failure in a control valve for controlling the amount of intake air into an engine, as described in JP-A-2002-285900. According to the known method, the control valve is operated by pressure in a vacuum tank. In a case in which the period of time during which a signal is being sent to the control valve for operating the control vale is longer than the period of time required for actually operating the control valve according to the operating state of the engine, the control valve is determined to have failed. Another known method is described in JP-A-H5-312066. According to this known method, when the engine revolution is between a first preset revolution and a second preset revolution, the opening state of the valve for switching between a long intake duct and a short intake duct is detected with an opening state detector. Then, according to the engine revolution, throttle opening degree, and the opening state of the valve, and based on a preset fuel injection rate, a fuel injection rate corresponding to the engine revolution at the time is calculated. Then, a fuel injection device is controlled to inject fuel into the engine at the calculated injection rate.
As an outboard motor is often operated at a high load and high revolution, the negative pressure type of actuator as disclosed in JP-A-2002-285900 sometimes cannot cope with the frequent switchover. On the other hand, the structure disclosed in JP-A-H5-312066 does not include controlling in an emergency, such as in the case of a failure of the valve, to compensate the fuel supply rate corresponding to the operation of the valve.